Medical handpieces, such as transnasal surgery drills, are conventionally used. This type of handpieces has a cutting tool that is rotatably driven by power transmitted from a drive source, such as a motor, for cutting an affected area. A transnasal surgery drill is used for cutting bone in front of the pituitary gland of a patient by inserting the drill through an expanded nasal cavity of the patient.
The applicant of the present application has filed a patent application regarding a medical handpiece, which is published as JP-2004-97790-A. The medical handpiece disclosed in this publication has a cutting tool having a flexible shank and a bur provided at the distal end of the shank for cutting an affected area. The cutting tool is inserted into a tubular sheath, and a tubular interposed member is interposed between the sheath and the shank of the cutting tool for preventing the shank from contacting the inner surface of the sheath. A handpiece body detachably holds the proximal end of the cutting tool for transmitting driving force from a drive source to the cutting tool. In this medical handpiece, the sheath, interposed member, and cutting tool are made flexible for a predetermined range, with the sheath being plastically deformed, the shank of the cutting tool being elastically deformed, and the interposed member being deformed following the deformation of the sheath and the shank.
In this medical handpiece, the interposed member is in the form of one continuous tubular body that is slightly shorter than a plastically deformable metallic pipe. Due to this structure, when the sheath is flexed for a relatively large angle, the shank of the cutting tool contacts the interposed member at a large pressure for a considerable length. This may cause undesirable vibration of the medical handpiece that deteriorates its operationability, and frictional heat that lowers the durability of the interposed member.
Depending on the affected area to be cut, a plurality of medical handpieces having sheathes of different lengths are used, and correspondingly, a plurality of cutting tools of different lengths are also provided. Medical practitioners have to handle such plurality of medical handpieces, and need to find which cutting tool corresponds to which handpiece, which is bothersome before and during surgery. In addition, the cutting tool, which is detachable for sterilization and cleaning and re-inserted for use, must be held in the handpiece body securely for safety.